With the diminishing supply of crude petroleum oil, use of renewable biomass as an energy source is becoming increasingly important for the production of liquid fuels and/or chemicals. The use of renewable biomass as an energy source may also allow for a more sustainable production of liquid fuels and more sustainable CO2 emissions that may help meet global CO2 emissions standards under the Kyoto protocol.
The fuels and/or chemicals from renewable biomass are often referred to as biofuels and/or biochemicals. Biofuels and/or biochemicals derived from non-edible biomass materials, such as cellulosic materials, are preferred as these do not compete with food production. These biofuels and/or biochemicals are also referred to as second generation or advanced biofuels and/or biochemicals. Most of these non-edible biomass materials, however, are solid materials that are cumbersome to convert into liquid fuels.
A well-known process to convert solid biomass material into a liquid is pyrolysis. By means of such pyrolysis of a solid biomass material a biomass-derived pyrolysis oil can be obtained. The energy density of the obtained pyrolysis oil is higher than that of the original solid biomass material. This has logistic advantages as it makes the pyrolysis oil more attractive for transport and/or storage than the original solid biomass material. Pyrolysis oils, however, can be less stable than conventional petroleum oils during storage and transport. Some of the compounds within the pyrolysis oil can react with each other during transport and/or storage and an undesired sludge may form. In order to improve the quality of biomass-derived pyrolysis oil, several manners of hydroprocessing have been suggested.
WO2011064172 describes a process including pyrolysis of biomass to obtain a pyrolysis oil and hydro-deoxygenation of this pyrolysis oil at a temperature in the range from 200 to 400° C. with a catalyst that may for example comprise metals of Group VIII and/or Group VIB of the Periodic Table of Elements. It is mentioned that the catalyst may possibly comprise nickel, copper and/or alloys or mixtures thereof, such as Ni—Cu on a catalyst carrier. Examples of carriers mentioned include alumna, amorphous silica-alumina, titania, silica and zirconia. As an example of suitable catalysts Ni—Cu/ZrO2 is mentioned.
WO2012/030215 describes a process for the hydrotreatment of vegetal biomass. It mentions that fast pyrolysis may be an attractive technology to transform difficult-to-handle biomass into a clean and uniform liquid, called pyrolysis oil. It further mentions that several processes have been proposed for upgrading the pyrolysis oil including hydrogenation under hydrogen pressure, catalytic cracking and high pressure thermal treatment. WO2012/030215 subsequently mentions that a problem with the catalysts known from the conventional refinery processes, such as nickel/molybdenum or cobalt/molybdenum on alumina supports, is that they are not meant to handle high water contents, whilst high water contents are common in pyrolysis oils. WO2012/030215 alleges that known catalysts will decay under reaction conditions, where a large amount of water is present and rather high temperatures are applied; and that the formation of coke may cause parts of the porous catalysts, prepared by impregnation of active metals on a porous support, to become inaccessible to the reactant, leading to quick catalyst inactivation as the catalyst support disintegrates, leaching of active components into the water and clogging of catalyst pores and or clogging of the reactor. According to WO2012/030215, there is a need for an improved catalyst and process for treating biomasses and a specific catalyst is claimed which is prepared by mixing hydrated metal oxides and a NH3 aqueous solvent, adding a solution of a C1-C6 alkyl silicate in a C1-C6 alkyl alcohol; impregnating with ZrO(NO3)2.2H2O and La(NO3)3.6H2O in water; drying the obtained product; and calcining the product at a temperature in the range from 350° C. to 900° C. WO2012/030215 states that the catalysts described therein are more effective in the hydrogenation of pyrolysis biomasses. The catalyst proposed in WO2012/030215, however, is too expensive to be used in a scaled up—commercial scale—conversion plant. Preparation of the catalyst as described in WO2012/030215 would require too large volumes of tetraalkylorthosilicates (in WO2012/030215 referred to as C1-C6 alkylsilicates, e.g. ethylsilicate), making the catalyst and process uneconomical. In addition, the presence of C1-C6-alkyl alkanols, such as ethanol, during the preparation of a catalyst as proposed in WO2012/030215 is undesirable. Ethanol is volatile, flammable, toxic and potentially carcinogenic and for all these reasons difficult to handle in a catalyst manufacturing environment.
It would therefore be an advancement in the art to provide a catalyst and process for converting a biomass-derived pyrolysis oil that would be more economical whilst still maintaining a good catalyst activity and avoiding any safety risks.